High frequency electrical circuit arrangement



Nov. 26, 1935. B] J, CHROMY v 2,022,459

HIGH FREQUENCY ELECTRICAL CIRCUIT ARRANGEMENT Filed Aug. 15, 1930FIYEQUE/VCY ,JL. C y;

Patented Nov. 26, 1935 UNITED STATES PATENT OFFICE Ben 'J. Chromy,Hopkins, Minn.

Application August 13, 1930, Serial No. 475,076 10 Claims. (Cl. 250-11)This invention relates to electrical circuit arrangements in general.More particularly this invention relates to electrical circuitarrangements employing selective frequency responsive elements whichmanifest substantial changes in their impedance characteristics atcertain determinable frequencies.

An object of this invention is to provide an arrangement for guidingmoving vessels, particularly aircraft, in accordance with signalingenergy transmitted from a radio beacon, said arrangement havingincorporated therein a balanced circuit which is adjusted to beunbalanced by signaling energy of a certain frequency or certainfrequencies which is intercepted by the radio receiving systemassociated with said arrangement.

A further object of this invention is to provide an arrangement whereinelectro-mechanically vibratile elements are employed to control theoperation of electrical circuits in accordance with electrical energycorresponding to a frequency or frequencies of the electro-mechanicallyvibratile elements.

Another object of this invention is to provide an arrangement whereinelectro-mechanically vibratile elements are employed to vary theimpedance of a circuit in accordance with electrical energy impressedupon them whereby the operation of electrical circuits is controlled inaccordance with the electrical energy impressed upon theelectro-mechanically vibratile elements.

Still another object is toprovide an arrangement wherein anelectro-mechanically vibratile element is associated with the inputcircuit of an electron discharge device to control the operation of theelectron discharge device in accordance with electrical energy ofcertain frequencies which are impressed upon the circuit of theelectro-mechanically vibratile element.

. Still a further object of this invention is to provide a balancedcircuit with an electro-mechanioally vibratile element for controllingthe operation of an electron discharge device circuit arrangement inaccordance with electrical energy of predetermined frequency which isimpressed upon the balanced circuit.

Still a further object of this invention is to provide an arrangement inwhich circuits including electro-mechanically vibratile elements controlthe operation of electron discharge devices in accordance with signalingenergy of a predetermined frequency for controlling the operation ofindicator devices.

Other and further objects of this invention will be more fullyunderstood from the following specification and claims.

In accordance with this invention one or more electro-mechanicallyvibratile elements, such as piezo-electric crystals or other elements,the elec- 5 trical impedance of which changes substantially at itsnatural period or periods or any harmonic thereof, are connected into abalanced circuit of the Wheatstone bridge type. Connections are providedbetween the balanced circuit and an 10 electron discharge device whichis to be controlled in operation by signaling energy corresponding to afrequency at which the impedance of the electro-mechanically vibratileelement changes substantially. A relay and an indicator, 15 which it isdesired to control in accordance with signaling energy of predeterminedfrequency, are connected into the output circuit of the electrondischarge device. An amplifier of any approved v design, such as areused in conjunction with radio 20 receiving systems, is arranged toamplify interceptedsignaling energy and to energize the bal-. ancedcircuit, with which the electro-mechani- .cally vibratile element isassociated. When signaling energy of the proper frequency is inter- 25cepted the balanced circuit is energized by energy of a correspondingfrequency and the. impedance of the electro-mechanically vibratileelement is caused to change and disturb the impedance balance of thebalanced circuit, whereupon the elec- 30 tron discharge deviceassociated with the balanced circuit is energized in accordance withsignaling energy of that proper frequency and the relay connected intothe output circuit of the electron discharge device is actuated. 35

Other features and details of this invention will be more readilyunderstood from the following specification and the drawing, in which:

Fig. 1 illustrates an embodiment of this invention; 40

Fig. 2 illustrates a modified form of the balanced circuit arrangement;

Fig. 3 illustrates another modified form of the balanced circuitarrangement;

Figs. 4 and 6 are curves illustrating operating characteristics ofcertain embodiments of this invention; and V Fig. 5 illustrates anothermodification of this invention.

Referring to Fig. 1 of the drawing in detail, reference numeral Idesignates a directional antenna of the loop type, which is coupled tothe substantially non-directional antenna 2 through the transformer 3. Avariable condenser 4 is connected into the circuit of the antenna 2. A v

ployed in radio receiving sets for amplifying high frequency signals.The transformer II is con nected to the output of the amplifier 9.Secondary winding I2 of the transformer I I is connected to the tuningcondenser I4 and the series condenser I5. The impedance units'l8, I9,2|, 22 and the electro-mechanically vibratile element 20 are connectedto form the legs of a balanced circuit which is connected to receivehigh frequency energy from the secondary winding I2.

The impedance units 32, 33, 34 and 36 and the electro-mechanicallyvibratile element 35 .are connected to form legs of another bridgecircuit which is associated with the secondary I3 of the transformer II.A tuning condenser I5 is connected across the secondary I3. Condenser I!is connected in series with the circuit of the tuned secondary I3 andthe bridge circuit including the electro-mechanically vibratile element35, and is selected to be of a relatively small capacity. Theadjustments of the condensers I6 and I! are not critical, however,especially in cases where the secondary windings I2 and I3 are made upof a relatively large number of turns in comparison to the number ofturns included in the primary of the transformer I I and the tuningcondensers I4 and I5 are omitted.

The condensers 22 and 36 are employed in the bridge circuitstofacilitate obtaining the proper phase relation between high frequencycurrents flowing thru the legs of the bridge circuits. Where it isdesired, additional variable condensers may be connected across each ofthe legs of the bridge circuits to facilitate obtaining the desiredbalanced conditions. In cases where noninductive resistance units areused as the impedance units I8, I9 and 2I of the first bridge circuitand as the impedance units 32, 33 and 34 of the second bridge circuit itmay not be necessary to shield these units by metallic shields,especially if the signaling frequencies at which this system is used arein the neighborhood of 500 kilocycles or less; however, in cases wherethe bridge circuits are made up into compact units, and. also in caseswhere the system is employed at signaling frequencies of three to fourthousand or more kilocycles, it is highly desirable that each leg of thebridge circuits be surrounded by metallic shields.

The input circuit of the electron discharge device 21 is connected tosymmetrical points of the bridge circuit which includes the element 20.The input circuit of the electron discharge device 4| is likewiseconnected to symmetrical points of the bridge circuit which includes theelement 35'. A relay 29 and a source of anode current supply 28 areconnected into the output circuit of the electron discharge device 21.The visual indicator 3B, which may be a glow lamp or an incandescentlamp, is connected to be energized from the source of current supply 3!when the relay 29 is energized in accordance with signalingvenergy. Therelay 43 and source of anode current supply 42 is connected into theoutput circuit ofthe electron discharge device 4|. The indicator 44,which is similar to the indicator 30, is connected to the current supplysource 3| to be energized when the circuit of relay 43 is energized inaccordance with signaling energy. The indicators 30 and 44 5 may beshaped in the form of the letters L and R, as shown in the drawing, inorder that deviation of a moving vessel, such as an aeroplane, employingthe system of this invention, to the left or right of the true coursemay be more readily ascertained accurately. These indicators 36 and 44may also be connected directly into the output circuits of the electrondischarge devices 2! and 4| and the relays 29 and 43 thus eliminated.

In operation the system of this invention illustrated in Fig. 1 isprovided with a pair of electromechanically vibratile elements and 35,such as piezo-electric crystals, which have frequency characteristicscorresponding to the signaling frequencies of the radio beacon inconjunction 20 with which this system is employed. Theseelectro-mechanically vibratile elements are connected into individualbridge circuits upon which signals, intercepted from the radio beaconare impressed. When signaling energy'having a frequency corresponding tothe frequency of the electro-mechanically vibratile element 20, forexample, the balance of the bridge circuit including thiselectro-mechanically vibratile element is disturbed and the anodecurrent of the electron 30,

lay 43 is caused to close the circuit of the indi- 4o,

cator 44.

The signals transmitted from the radio beacon may be transmitted in tworelatively narrow beams parts of which may be made to traverse the samearea. The part of the beams .of sig- 5 naling energy traversing the samearea consists of signals of both of the radio beacon frequencies; thatis, frequencies corresponding to those of both of theelectro-mechanically vibratile elements 20 and 35. When the moving craftemploying the system of this invention is moving in the zone defined bythe coinciding part of the beams, then both of the indicators 30 and 44are energized, since signals of frequencies corresponding to both of theelectro-mechanically vibratile elements 20 and 35 are intercepted.

In Fig.2 is illustrated a modified form of electro-mechanicallyvibratile element arrangement. Impedance units BI, 62, and 63, which arepreferably in the form of non-inductive resistance units, are connectedinto a bridge circuit, to

gether with the electro-mechanically vibratile elements f65,-66 and 61.A variable capacity 64 is connected in parallel with the impedance unit63 to facilitate obtaining a balanced condition in 65 the bridgecircuit. The electro-mechanically vibratile elements 65, 66 and B! maybe of the quartz piezo-electric crystal type each ground to a differentfrequency. By employing a plurality of elements each of a differentfrequency char- 70 acteristic in one leg of the bridge circuit the balanced condition of the bridge circuit may be disturbed by impressingvoltages of frequencies of any one of the elements upon the bridgecircuit, and the electron discharge device 60 may be 7 caused to operatecircuits associated with its output circuits by any one of the bridgebalance disturbing frequencies. In place of the electromechanicallyvibratile elements 65, 66 and 61 a single electro-mechanically vibratileunit ground in step formation as disclosed in Patent: No. 1,717,451 toAugust Hund may be employed. Where, however, it is desired to obtain acondition in which the balance of the bridge circuit may be disturbed atany frequency throughout a band of frequencies, a piezo-electriccrystal, gradually tapered along its X-axis, may be employed.

Shielded impedance units of the inductance coil type may be employed inthe balanced bridge circuit, as illustrated in Fig. 3 of the drawing.The secondary I2 of the transformer H is connecmd through the condenserIE to the bridge circuit which is made up of the impedance coils 85, 86,8'! and 88. Electra-mechanically vibratile element 89 is connectedacross the coil 88. Electron discharge device 98 is connected betweenelectrically symmetrical points of the impedance bridge circuit. Asuitable relay is connected into the output circuit of the electrondischarge device 98, as illustrated in Fig. 1 of the drawing. Suitableshields A, B, C and D are provided to the impedance coils 85, 86, 81 and88, respectively, to facilitate balancing the bridge circuit. In orderto balance the bridge circuit, the impedance coils may be made variableor in the form of variometer units or a small variable condenser may beconnected across each of the impedance coils, as illustrated in Fig. 5.It is, of course, not necessary to connect the variable condenser acrossthe entire impedance coil in each case, since these condensers may beconnected across only a small portion of each coil. A second bridgecircuit made up of impedance coils and an electro-mechanically vibratileunit is connected across the secondary I3 of the transformer H.

I3 may be made up of a relatively large number of turns of wire and theusual tuning condensers, such as employed in the form of this inventionillustrated in Fig. 1 of the drawing, eliminated. Only one of thesecondary windings I2 and I3 need be employed in cases where it isdesired to reduce the weight of apparatus used, since both of the bridgecircuits may be connected to one secondary thru proper condensers.

In Fig. 4 of the drawing is illustrated an anode current, frequencycharacteristic of the electron discharge device 90 obtained in caseswhere only one electro-mechanically vibratile element was employed inthe bridge circuit, as illustrated in Fig. 3 of the drawing. From thischaracteristic curve it is seen that the flow of anode current is causedto increase substantially when voltages of frequencies slightly above orbelow the frequency of the electro-mechanically' vibratile element areimpressed upon the bridge circuit. The relay connected into the outputcircuit of the electron discharge device is caused to operate by theincreasing anode current which is obtained on either side of thefrequency of the electro' mechanically vibratile element. The frequencyband over which the increased anode current is obtained may be adjustedin width by adjusting the impedance frequency characteristic of thebridge circuit with which the electro-mechanically vibratile element isassociated. A much narrower band is obtained by tuning the inductanceunits employed in the individual legs of the bridge circuit. Anembodiment of this These secondary windings I2 and invention in whichtuned inductance units I85, I01, I09 and'II2 are employed in thebalanced bridge circuit is illustrated in Fig. 5 of the drawing. Tuningcondensers I88, I08, III! and H3 are connected to the inductance unitsI85, I81, I89 and II 2, respectively. Electro-mechanically vibratileelements III and H4 are connected across the inductances H8 and H2.These electro-mechanically vibratile elements may be connected acrosssections of these inductances only if desired.

When two electro-mechanically vibratile elements Ill and H4 areconnected to the bridge circuit symmetrically with respect to the gridelectrode connection, the anode current, exciting voltage frequencycharacteristic illustrated in Fig. 6 of the drawing, is obtained incases where the frequency of one of the electro-mechanically vibratileelements is slightly higher than the frequency of the otherelectro-mechanically vibratile element. Only one point at which theanode current rises to a value substantially in excess of the normalanode current is obtained in the anode current, exciting voltagefrequency characteristic when two electro-mechanically vibratileelements, bearing the proper frequency relation to each other, areemployed in the bridge circuit. .fIhe variable condensers I86, H38, H0and H3, which are associated with the legs of the tuned bridge circuit,must be adjusted so that the bridge is balanced at a frequency slightlyabove the frequency of the higher frequency electro-mechanicallyvibratile element or at a frequency slightly below the frequency of thelower frequency electro-mechanically vibratile element in order thatthecharacteristic curve illustrated in Fig. 6 may be obtained. In order toobtain the characteristic illustrated in Fig. 6, the inductance andcapacity units forming the legs of the bridge circuit must be relativelysharply tuned. These inductance and capacity units may, however, beplaced into small aluminum shieldswithout destroying their selectiveadjustment if the inductance units are small in diameter and thevariable tuning condensers employed are small.

It will be observed that other modifications of this invention may bereadily made without departing from the scope. or spirit thereof as setforth in the foregoing specification; and that, therefore, I do notdesire to limit this invention to the exact details'as set forth exceptin so far as those details are defined in the appended claims.

What I claim and desire to secure by Letters Patent of the United Statesis as follows:

1. In signaling systems, the combination of an antenna, signalreceiving. apparatus, a pair of vibratory elements having differentfrequency characteristics, means for energizing said vibratory elementsin accordance with signaling energy of slightly different frequencies,indicating means connected to be energized in accordance with saidsignaling energy and means connected between each of said vibratoryelements and said indicating means for producing a uni-directionalcurrent in accordance with signaling energy impressed upon the circuitsthereof.

2. In radio receiving apparatus of the class described and for thepurposes set forth, a plurality of vibratory members. each of saidmembers having a natural period of vibration, exciting means therefor,signal-intercepting means for energizing said exciting means inaccordance with signals of different frequencies radiated fromremotesignal-transmitting apparatus and having relative intensity dependentupon the position of said signal-intercepting means with respect to thesignal-transmitting apparatus, the natural period of each of saidmembers corresponding to one of said frequencies whereby each membervibrates with amplitude dependent upon the intensity of the suppliedcurrent having its respective frequency, means associated with eachvibratory member for producing a unidirectional electro-motive forcehaving magnitude dependent upon the amplitude of vibration of therespective vibratory member, and means responsive to the relativemagnitudes of said unidirectional electromotive forces.

3. In radio-receiving apparatus of the class described and for thepurposes set forth, a plurality of vibratory members, each of saidmembers having a natural period of vibration, exciting means therefor,means for intercepting and supplying to said exciting means a pluralityof currents generated by remote radio-transmitting apparatus, saidcurrents having different frequencies and having relative intensitydependent upon the position of said intercepting means with respect tothe radio-transmitting apparatus, the natural period of each of saidmembers corresponding to one of said frequencies whereby each membervibrates with amplitude dependent upon the intensity of the suppliedcurrent having its respective frequency, means associated with eachvibratory member for producing a unidirectional electromotive forcehaving magnitude dependent upon the amplitude of vibration of therespective vibratory member, and means responsive to the relativemagnitudes of said unidirectional electromotive forces.

4. In radio-receiving apparatus of the class described and for thepurposes set forth, a plurality of vibratory members, each of saidmembers having a natural period of vibration, exciting means therefor,signal-intercepting means for energizing said exciting means inaccordance with signals of different frequencies radiated from remotesignal-transmitting apparatus and having relative intensity dependentupon the position of said signal-intercepting means with respect to thesignal-transmitting apparatus, the natural period of each of saidmembers corresponding to one of said frequencies whereby each membervibrates with amplitude dependent upon the intensity of the suppliedcurrent having its respective frequency, means associated with eachvibratory member for producing a unidirectional electromotive forcehaving magnitude dependent upon the amplitude of vibration of therespective vibratory member, relay means responsive to saidunidirectional electromotive forces,.and indicating means controlled bysaid relay means.

5. In position-determining apparatus of the radio-receiver type for usein conjunction with remote radio-transmitting apparatus setting upsignal fields of distinct positional relationship and distinct frequencycharacteristics, the combination of means for intercepting said signals,means for increasing the amplitude of the intercepted signalling energy,a plurality of electromechanically vibratile elements respectivelyresonant to the respective signal frequencies and respectively energizedthereby, balanced circuits respectively coupled with saidelectro-mechanically vibratile elements, a rectifier connected to eachof said balanced circuits, and indicating means energized in accordancewith current flow through said rectifiers.

6. In signal-receiving apparatus of the class described for use inconjunction with radiotransmitting apparatus setting up signals of twoor more distinct characteristics, antenna means for interceptingsuch-signals of distinct characteristics, means for amplifying saidsignals when intercepted, a plurality of circuits each of which isnormally electrically balanced, said circuits being coupled to saidamplifying means, a plurality of means, one in each of said balancedcircuits and constituting a part thereof, each of which last-mentionedmeans is preferentially responsive to intercepted signals having adifferent one of said distinct characteristics, an electron dischargedevice connected to each of said balanced circuits for energization uponthe unbalancing of its associated circuit, and indicating meansconnected to the output circuits of each of said electron dischargedevices for indicating when radio signals of each of said distinctcharacteristics are intercepted.

7. In signal-receiving apparatus of the class described for use inconjunction with radiotransmitting apparatus setting up, signals of twoor more distinct characteristics, antenna means for interceptingsuchsignals of distinct characteristics, means for amplifying saidsignals when intercepted, a plurality of circuits each of which isnormally electrically balanced, said circuits being coupled to saidamplifying means, a plurality of electro-mechanically vibratile means,one in each of said balanced circuits and constituting a part thereof,each of which electro-mechanically vibratile means is preferentiallyresponsive to intercepted signals having a different one of saiddistinct characteristics, an electron discharge device connected to eachof said balanced circuits for energization upon the unbalancing of theassociated circuit, and indicating means connected to the outputcircuits of each of said electron discharge devices for indicating whenradio signals of each of said distinctcharacteristics are intercepted.

8. In signal receiving apparatus of the class described, means forreceiving signaling energy, amplifyingmeans connected to said firstmeans, a pair of Wheatstone bridge circuits, means for selectivelyunbalancing one or the other of said bridge circuits in accordance withsignaling energy of distinct predetermined characteristics, electrondischarge devices connected to said bridge circuits and indicating meansconnected to the output circuitsof said electron discharge devices toindicate the unbalancing of said bridge circuits.

9..In.signal receiving apparatus of the class described adapted to beemployed for determining direction or course with respect to remotesignaling means transmitting signaling energies having two or moredistinct frequency components, means for intercepting said'signalingenergies, means for increasing the amplitude of said interceptedsignaling energies, a plurality. of vibratory, members resonant to saidfrequency components, a plurality of Wheatstone bridge circuits eachincluding one of said vibratory members in at least one of the legsthereof, said Wheatstone bridge circuits being connected tofirst-mentioned series of vibratory members in one leg thereof and oneof said second-mentioned series of vibratory members in another legthereof, said Wheatstone bridge circuits being connected to saidamplifying means whereby signaling energy is impressed upon saidvibratory members, electron discharge devices connected to saidWheatstone bridge circuits, and indicating means connected to the outputcircuits of said electron discharge devices.

BEN J. CHROMY.

